Kinetic Theory Gases

In this iit jee physics video lectures, we are going to study about kinetic theory of gasses. In the video above we are going to discuss postulates of KTG, and pressure of an ideal gas.

So let’s discuss the postulates of KTG. The 5 postulates are (These are applicable only for ideal gasses and not real gasses);

Gas has no shape or size and it acquires all the available space to it. The molecules are of a point mass, rigid and are similar in shape. There is no interaction between the molecules. This is because there is a big empty space between the molecules.

The gas molecules are always in motion and collide in elastically with each other and the walls of the container. Due to the collision, the each molecule exerts pressure on the walls of the container.

Further, in this jee physics video we have derives the equation of pressure of an ideal gas. This is done by taking a cube whose side is‘d’. Now let’s take a molecule of a gas whose velocity is ‘v’ and its components are vy along the x-axis, vy along the y-axis and vz along the z-axis. In the given experiment we have taken

m as the mass of the molecule

V as the volume = d3

N as the total number of molecules in the cube.

In Next video for jee physics, we are going to find the change in momentum of a molecule of mass m moving with velocity vx. The initial momentum is mVx and the final momentum is (-mVx). Further, we find that ∆P= (-2mVx). This is the change in momentum in the case of a single collision. Further, we found the number of collisions in unit time is n. In the end, we found out that n =2NmVx/2d, where d is the distance travelled. Now the force on the wall is, F=NmVx2/d so as we know that pressure is force divided by area. Therefore,